这个插件可以满足我的目的
Media Sync
https://wordpress.org/plugins/media-sync/
This plugin allows you to examine all files within the uploads directory to determine which ones are present in the Media Library and which ones are just sitting there unused. You can then choose the files you want to import into the database, thereby including them in the Media Library.
Moreover, you can utilize FTP to upload files directly to the uploads directory and subsequently add these files to the Media Library avoiding any file size limitations.
这个plugin的pro version要40美金